import { writeFileSync } from "node:fs";
import { join } from "node:path";
import { type } from "arktype";
import { log } from "../utils/log.ts";
import type { ToolContext } from "./server.ts";
import { execute, tool } from "./shared.ts";

// GraphQL query to fetch all review threads for a PR with full comment history
export const REVIEW_THREADS_QUERY = `
query ($owner: String!, $name: String!, $prNumber: Int!) {
  repository(owner: $owner, name: $name) {
    pullRequest(number: $prNumber) {
      reviewThreads(first: 100) {
        nodes {
          id
          path
          line
          startLine
          diffSide
          isResolved
          isOutdated
          comments(first: 50) {
            nodes {
              fullDatabaseId
              body
              createdAt
              diffHunk
              line
              startLine
              originalLine
              originalStartLine
              author { login }
              pullRequestReview {
                databaseId
                author { login }
              }
              reactionGroups {
                content
                reactors(first: 10) {
                  nodes {
                    ... on Actor { login }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}
`;

export type ReviewThreadComment = {
  fullDatabaseId: string | null;
  body: string;
  createdAt: string;
  diffHunk: string;
  line: number | null;
  startLine: number | null;
  originalLine: number | null;
  originalStartLine: number | null;
  author: { login: string } | null;
  pullRequestReview: {
    databaseId: number | null;
    author: { login: string } | null;
  } | null;
  reactionGroups: Array<{
    content: string;
    reactors: { nodes: Array<{ login: string } | null> | null } | null;
  }> | null;
};

export type ReviewThread = {
  id: string;
  path: string;
  line: number | null;
  startLine: number | null;
  diffSide: "LEFT" | "RIGHT";
  isResolved: boolean;
  isOutdated: boolean;
  comments: {
    nodes: (ReviewThreadComment | null)[] | null;
  } | null;
};

export type ReviewThreadsQueryResponse = {
  repository: {
    pullRequest: {
      reviewThreads: {
        nodes: (ReviewThread | null)[] | null;
      } | null;
    } | null;
  } | null;
};

// extract exactly the commented line range from diffHunk, plus context
const CONTEXT_PADDING = 3;

function extractCommentedLines(
  diffHunk: string,
  startLine: number | null,
  endLine: number | null,
  side: "LEFT" | "RIGHT"
): string {
  const lines = diffHunk.split("\n");
  if (lines.length <= 1) return diffHunk;

  const header = lines[0];
  const contentLines = lines.slice(1);

  // parse header: @@ -old_start,old_count +new_start,new_count @@
  const headerMatch = header.match(/@@ -(\d+)(?:,\d+)? \+(\d+)(?:,\d+)? @@/);
  if (!headerMatch) return diffHunk;

  const hunkOldStart = parseInt(headerMatch[1], 10);
  const hunkNewStart = parseInt(headerMatch[2], 10);

  // LEFT = old file (deletions), RIGHT = new file (additions)
  const hunkStart = side === "LEFT" ? hunkOldStart : hunkNewStart;
  const commentStart = startLine ?? endLine ?? hunkStart;
  const commentEnd = endLine ?? commentStart;

  // walk through diff lines, tracking line numbers for both old and new files
  // - lines: old file only (LEFT)
  // + lines: new file only (RIGHT)
  // context lines: both files
  type DiffLine = { text: string; lineNum: number | null };
  const diffLines: DiffLine[] = [];
  let oldLineNum = hunkOldStart;
  let newLineNum = hunkNewStart;

  for (const line of contentLines) {
    const prefix = line[0];
    if (prefix === "-") {
      // deletion - only has old line number
      diffLines.push({ text: line, lineNum: side === "LEFT" ? oldLineNum : null });
      oldLineNum++;
    } else if (prefix === "+") {
      // addition - only has new line number
      diffLines.push({ text: line, lineNum: side === "RIGHT" ? newLineNum : null });
      newLineNum++;
    } else {
      // context - has both line numbers
      diffLines.push({ text: line, lineNum: side === "LEFT" ? oldLineNum : newLineNum });
      oldLineNum++;
      newLineNum++;
    }
  }

  // find lines for comment range with context
  const targetStart = commentStart - CONTEXT_PADDING;
  const targetEnd = commentEnd;

  const result: string[] = [];
  let truncatedBefore = 0;

  for (let i = 0; i < diffLines.length; i++) {
    const dl = diffLines[i];
    // include if: within target range, OR it's an "other side" line adjacent to included lines
    const inRange = dl.lineNum !== null && dl.lineNum >= targetStart && dl.lineNum <= targetEnd;
    // include opposite-side lines if they're between included lines
    const adjacentOtherSide = dl.lineNum === null && result.length > 0 && i < diffLines.length - 1;

    if (inRange || adjacentOtherSide) {
      result.push(dl.text);
    } else if (result.length === 0) {
      truncatedBefore++;
    }
  }

  if (truncatedBefore > 0) {
    return `${header}\n... (${truncatedBefore} lines above) ...\n${result.join("\n")}`;
  }
  return `${header}\n${result.join("\n")}`;
}

// parsed hunk from a unified diff
export type ParsedHunk = {
  header: string;
  oldStart: number;
  oldCount: number;
  newStart: number;
  newCount: number;
  content: string[];
};

// parse a full file patch into individual hunks
export function parseFilePatches(patch: string): ParsedHunk[] {
  const hunks: ParsedHunk[] = [];
  const lines = patch.split("\n");

  let currentHunk: ParsedHunk | null = null;

  for (const line of lines) {
    const hunkMatch = line.match(/@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@/);
    if (hunkMatch) {
      if (currentHunk) hunks.push(currentHunk);
      currentHunk = {
        header: line,
        oldStart: parseInt(hunkMatch[1], 10),
        oldCount: parseInt(hunkMatch[2] ?? "1", 10),
        newStart: parseInt(hunkMatch[3], 10),
        newCount: parseInt(hunkMatch[4] ?? "1", 10),
        content: [],
      };
    } else if (currentHunk) {
      currentHunk.content.push(line);
    }
  }
  if (currentHunk) hunks.push(currentHunk);

  return hunks;
}

// find hunks that overlap with a line range (for LEFT or RIGHT side)
function findOverlappingHunks(
  hunks: ParsedHunk[],
  startLine: number,
  endLine: number,
  side: "LEFT" | "RIGHT"
): ParsedHunk[] {
  return hunks.filter((hunk) => {
    const hunkStart = side === "LEFT" ? hunk.oldStart : hunk.newStart;
    const hunkCount = side === "LEFT" ? hunk.oldCount : hunk.newCount;
    const hunkEnd = hunkStart + hunkCount - 1;

    // check for overlap: ranges overlap if start1 <= end2 && start2 <= end1
    return startLine <= hunkEnd && hunkStart <= endLine;
  });
}

// extract diff content from multiple hunks for a comment range
function extractFromFilePatches(
  hunks: ParsedHunk[],
  startLine: number,
  endLine: number,
  side: "LEFT" | "RIGHT"
): string {
  const overlapping = findOverlappingHunks(hunks, startLine, endLine, side);

  if (overlapping.length === 0) {
    return `(no diff hunks found for lines ${startLine}-${endLine})`;
  }

  if (overlapping.length === 1) {
    // single hunk - use existing extraction logic
    const hunk = overlapping[0];
    const fullHunk = hunk.header + "\n" + hunk.content.join("\n");
    return extractCommentedLines(fullHunk, startLine, endLine, side);
  }

  // multiple hunks - combine them with gap indicators
  const result: string[] = [];
  let prevHunkEnd = 0;

  for (let i = 0; i < overlapping.length; i++) {
    const hunk = overlapping[i];
    const hunkStart = side === "LEFT" ? hunk.oldStart : hunk.newStart;
    const hunkCount = side === "LEFT" ? hunk.oldCount : hunk.newCount;
    const hunkEnd = hunkStart + hunkCount - 1;

    // add gap indicator if there's a gap between hunks
    if (i > 0 && hunkStart > prevHunkEnd + 1) {
      const gapSize = hunkStart - prevHunkEnd - 1;
      result.push(`\n... (${gapSize} unchanged lines) ...\n`);
    }

    // add the hunk header and content
    result.push(hunk.header);
    result.push(...hunk.content);

    prevHunkEnd = hunkEnd;
  }

  return result.join("\n");
}

export const GetReviewComments = type({
  pull_number: type.number.describe("The pull request number"),
  review_id: type.number.describe("The review ID to get comments for"),
  approved_by: type.string
    .describe(
      "Optional GitHub username - only return threads where this user gave a 👍 to at least one comment"
    )
    .optional(),
});

function hasThumbsUpFrom(comment: ReviewThreadComment, username: string): boolean {
  if (!comment.reactionGroups) return false;
  const thumbsUp = comment.reactionGroups.find((g) => g.content === "THUMBS_UP");
  if (!thumbsUp?.reactors?.nodes) return false;
  return thumbsUp.reactors.nodes.some((r) => r?.login === username);
}

function threadHasThumbsUpFrom(thread: ReviewThread, username: string): boolean {
  const comments = thread.comments?.nodes ?? [];
  return comments.some((c) => c && hasThumbsUpFrom(c, username));
}

/**
 * formats thread blocks into markdown with TOC and line numbers.
 * extracted for testability.
 */
export function formatReviewThreads(
  threadBlocks: Array<{ path: string; lineRange: string; content: string[] }>,
  header: { pullNumber: number; reviewId: number; reviewer: string }
) {
  // header section takes: title (1) + blank (1) + "## TOC" (1) + blank (1) + N TOC entries + blank (1) + "---" (1) + blank (1)
  const tocHeaderLines = 4;
  const tocFooterLines = 3;
  let currentLine = tocHeaderLines + threadBlocks.length + tocFooterLines + 1;

  const tocEntries: string[] = [];
  const threadLines: string[] = [];

  for (const block of threadBlocks) {
    const startLine = currentLine;
    const actualLineCount = block.content.reduce((sum, line) => sum + line.split("\n").length, 0);
    const endLine = currentLine + actualLineCount - 1;
    tocEntries.push(`- ${block.path}:${block.lineRange} → lines ${startLine}-${endLine}`);
    threadLines.push(...block.content);
    currentLine += actualLineCount;
  }

  const lines: string[] = [];
  lines.push(
    `# Review Threads (${threadBlocks.length}) for PR #${header.pullNumber} - Review ${header.reviewId} by ${header.reviewer}`
  );
  lines.push("");
  lines.push("## TOC");
  lines.push("");
  lines.push(...tocEntries);
  lines.push("");
  lines.push("---");
  lines.push("");
  lines.push(...threadLines);

  return {
    toc: tocEntries.join("\n"),
    content: lines.join("\n"),
  };
}

/**
 * builds thread blocks from review threads and file patches.
 * extracted for testability.
 */
export function buildThreadBlocks(
  threads: ReviewThread[],
  filePatchMap: Map<string, ParsedHunk[]>,
  reviewId: number
) {
  // get reviewer from first matching comment
  const firstMatchingComment = threads[0]?.comments?.nodes?.find(
    (c) => c?.pullRequestReview?.databaseId === reviewId
  );
  const reviewer = firstMatchingComment?.pullRequestReview?.author?.login ?? "unknown";

  // sort threads by file path, then by line number
  threads.sort((a, b) => {
    const pathCmp = a.path.localeCompare(b.path);
    if (pathCmp !== 0) return pathCmp;
    const aLine = a.startLine ?? a.line ?? 0;
    const bLine = b.startLine ?? b.line ?? 0;
    return aLine - bLine;
  });

  const threadBlocks: Array<{ path: string; lineRange: string; content: string[] }> = [];

  for (const thread of threads) {
    const allComments = (thread.comments?.nodes ?? []).filter(
      (c): c is ReviewThreadComment => c !== null
    );
    if (allComments.length === 0) continue;

    // get line info from thread, or fall back to first comment's line info
    const firstComment = allComments[0];
    const line =
      thread.line ?? firstComment?.line ?? firstComment?.originalLine ?? thread.startLine ?? 0;
    const startLine =
      thread.startLine ?? firstComment?.startLine ?? firstComment?.originalStartLine ?? line;
    const lineRange = startLine === line ? `${line}` : `${startLine}-${line}`;
    const block: string[] = [];

    // header with file:line range and status
    const status = thread.isResolved ? " [RESOLVED]" : thread.isOutdated ? " [OUTDATED]" : "";
    block.push(`## ${thread.path}:${lineRange}${status}`);
    block.push("");

    // show all comments in the thread (full conversation history)
    for (const comment of allComments) {
      const author = comment.author?.login ?? "unknown";
      const isTargetReview = comment.pullRequestReview?.databaseId === reviewId;
      const marker = isTargetReview ? " *" : "";

      block.push(
        `\`\`\`\`comment author=${author} id=${comment.fullDatabaseId ?? "unknown"} review=${comment.pullRequestReview?.databaseId ?? "unknown"} thread=${thread.id}${marker}`
      );
      block.push(comment.body || "(no comment body)");
      block.push("````");
      block.push("");
    }

    // diff context
    const fileHunks = filePatchMap.get(thread.path);
    const firstCommentWithHunk = allComments.find((c) => c.diffHunk);
    let diffContent: string | null = null;

    if (fileHunks && fileHunks.length > 0) {
      const overlapping = findOverlappingHunks(fileHunks, startLine, line, thread.diffSide);
      if (overlapping.length > 0) {
        diffContent = extractFromFilePatches(fileHunks, startLine, line, thread.diffSide);
      }
    }

    if (!diffContent && firstCommentWithHunk) {
      diffContent = extractCommentedLines(
        firstCommentWithHunk.diffHunk,
        startLine,
        line,
        thread.diffSide
      );
    }

    if (diffContent) {
      block.push(`\`\`\`diff file=${thread.path} lines=${lineRange} side=${thread.diffSide}`);
      block.push(diffContent);
      block.push("```");
      block.push("");
    } else {
      block.push(`\`\`\`diff file=${thread.path} lines=${lineRange} side=${thread.diffSide}`);
      block.push(`(no diff context available - comment on unchanged lines)`);
      block.push("```");
      block.push("");
    }

    threadBlocks.push({ path: thread.path, lineRange, content: block });
  }

  return { threadBlocks, reviewer };
}

export function GetReviewCommentsTool(ctx: ToolContext) {
  return tool({
    name: "get_review_comments",
    description:
      "Get review comments for a pull request review with full thread context. " +
      "When approved_by is provided, only returns threads where that user gave a 👍 to at least one comment. " +
      "Returns a TOC and commentsPath pointing to a markdown file with full comment details.",
    parameters: GetReviewComments,
    execute: execute(async (params) => {
      // fetch all review threads for the PR via GraphQL
      const response = await ctx.octokit.graphql<ReviewThreadsQueryResponse>(REVIEW_THREADS_QUERY, {
        owner: ctx.repo.owner,
        name: ctx.repo.name,
        prNumber: params.pull_number,
      });

      const allThreads = response.repository?.pullRequest?.reviewThreads?.nodes ?? [];

      // filter to threads where at least one comment belongs to the target review
      let threadsForReview = allThreads.filter((thread): thread is ReviewThread => {
        if (!thread?.comments?.nodes) return false;
        return thread.comments.nodes.some(
          (c) => c?.pullRequestReview?.databaseId === params.review_id
        );
      });

      // filter by approved_by if specified
      if (params.approved_by) {
        threadsForReview = threadsForReview.filter((thread) =>
          threadHasThumbsUpFrom(thread, params.approved_by as string)
        );
      }

      if (threadsForReview.length === 0) {
        return {
          review_id: params.review_id,
          pull_number: params.pull_number,
          reviewer: "unknown",
          threadCount: 0,
          commentsPath: null,
          toc: null,
          instructions: params.approved_by
            ? `no threads with 👍 from ${params.approved_by}`
            : "no threads found for this review",
        };
      }

      // fetch full file patches for better multi-hunk context
      const prFilesResponse = await ctx.octokit.rest.pulls.listFiles({
        owner: ctx.repo.owner,
        repo: ctx.repo.name,
        pull_number: params.pull_number,
      });
      const filePatchMap = new Map<string, ParsedHunk[]>();
      for (const file of prFilesResponse.data) {
        if (file.patch) {
          filePatchMap.set(file.filename, parseFilePatches(file.patch));
        }
      }

      // build thread blocks
      const { threadBlocks, reviewer } = buildThreadBlocks(
        threadsForReview,
        filePatchMap,
        params.review_id
      );

      // format thread blocks into markdown with TOC
      const formatted = formatReviewThreads(threadBlocks, {
        pullNumber: params.pull_number,
        reviewId: params.review_id,
        reviewer,
      });

      // write to temp file
      const tempDir = process.env.PULLFROG_TEMP_DIR;
      if (!tempDir) {
        throw new Error("PULLFROG_TEMP_DIR not set");
      }
      const filename = `review-${params.review_id}-threads.md`;
      const commentsPath = join(tempDir, filename);
      writeFileSync(commentsPath, formatted.content);
      log.debug(`wrote ${threadBlocks.length} threads to ${commentsPath}`);

      return {
        review_id: params.review_id,
        pull_number: params.pull_number,
        reviewer,
        threadCount: threadBlocks.length,
        commentsPath,
        toc: formatted.toc,
        instructions:
          `the file at commentsPath contains ${threadBlocks.length} review threads with full conversation history. ` +
          `comments marked with * are from the target review (${params.review_id}). ` +
          `the TOC shows each thread's file:line and the line number where it appears in the file. ` +
          `to read a specific thread, use: grep -A 50 "^## <file:line>" ${commentsPath} ` +
          `(replace <file:line> with the path from the TOC, e.g. "^## action/utils/foo.ts:42"). ` +
          `address each thread in order, working through one file at a time.`,
      };
    }),
  });
}

export const ListPullRequestReviews = type({
  pull_number: type.number.describe("The pull request number to list reviews for"),
});

export function ListPullRequestReviewsTool(ctx: ToolContext) {
  return tool({
    name: "list_pull_request_reviews",
    description:
      "List all reviews for a pull request. Returns all reviews including approvals, request changes, and comments.",
    parameters: ListPullRequestReviews,
    execute: execute(async (params) => {
      const reviews = await ctx.octokit.paginate(ctx.octokit.rest.pulls.listReviews, {
        owner: ctx.repo.owner,
        repo: ctx.repo.name,
        pull_number: params.pull_number,
      });

      return {
        pull_number: params.pull_number,
        reviews: reviews.map((review) => ({
          id: review.id,
          node_id: review.node_id,
          body: review.body,
          state: review.state,
          user: review.user?.login,
          submitted_at: review.submitted_at,
        })),
        count: reviews.length,
      };
    }),
  });
}

const RESOLVE_REVIEW_THREAD_MUTATION = `
mutation($threadId: ID!) {
  resolveReviewThread(input: {threadId: $threadId}) {
    thread {
      id
      isResolved
    }
  }
}
`;

export const ResolveReviewThread = type({
  thread_id: type.string.describe("The GraphQL node ID of the review thread to resolve"),
});

export function ResolveReviewThreadTool(ctx: ToolContext) {
  return tool({
    name: "resolve_review_thread",
    description:
      "Mark a review thread as resolved using GitHub's GraphQL API. " +
      "Only call this after addressing the review feedback, implementing fixes, testing them, and posting a reply. " +
      "Do not resolve threads that are already resolved, threads where no action was taken, or threads where you disagree with the feedback.",
    parameters: ResolveReviewThread,
    execute: execute(async (params) => {
      try {
        const response = await ctx.octokit.graphql<{
          resolveReviewThread: {
            thread: {
              id: string;
              isResolved: boolean;
            };
          };
        }>(RESOLVE_REVIEW_THREAD_MUTATION, {
          threadId: params.thread_id,
        });

        const thread = response.resolveReviewThread.thread;
        log.debug(`resolved thread ${thread.id}, isResolved=${thread.isResolved}`);

        return {
          thread_id: thread.id,
          is_resolved: thread.isResolved,
          success: true,
          message: "Thread resolved successfully",
        };
      } catch (error) {
        // handle common error cases gracefully
        const errorMessage = error instanceof Error ? error.message : String(error);
        const isResolved =
          errorMessage.includes("already resolved") || errorMessage.includes("isResolved");

        const message = isResolved
          ? `thread ${params.thread_id} was already resolved`
          : `failed to resolve thread ${params.thread_id}: ${errorMessage}`;
        log.warning(message);

        return {
          thread_id: params.thread_id,
          is_resolved: isResolved,
          success: isResolved,
          message,
        };
      }
    }),
  });
}